TOLEDO, Ohio (AP) — In his warm-up for the Democratic National Convention, President Barack Obama is tangling with a couple of rivals, only one named Mitt. The other is voter apathy, especially among the young.

Obama's pre-convention tour of battleground states has been heavy on college crowds, where he's implored supporters to register and vote by painting the choice in stark terms: It's his education tax credits versus Mitt Romney's tax breaks for the rich; his "Obamacare" versus "Romney doesn't care," his "forward" versus "same old."

And when those crowds boo the references to Romney, Obama tells them to convert that negative energy into votes Election Day.

Obama addresses a United Auto Workers Labor Day rally in Toledo on Monday before getting his first look at the aftermath of Hurricane Isaac in a stricken parish outside New Orleans. He's to meet emergency personnel who've been laboring since the storm hit last week to restore power and tend thousands of evacuees from flooded lands.

In Boulder, Colo., on Sunday, Obama warned a college crowd that "the other side is going to spend more money than we've ever seen in our lives, with an avalanche of attack ads and insults and making stuff up, just making stuff up."

"What they're counting on is that you get so discouraged by this, that at a certain point you just say, you know what, I'm going to leave it up to somebody else." Obama did not mention his own side's arsenal of negative advertising.

The Republican convention behind him, Romney was staying low for a few days, ceding the political attention to his rival and preparing for the October debates as Democratic conventioneers gathered for the opening of their event Tuesday in Charlotte.

Younger voters gave Obama a big boost four years ago and he can ill afford to see their support drop off in a tight election where the sluggish economy is the dominant issue in the nation and a specific drag to many young people coming out of college or trying to afford it.

But his campaign surely has a more immediate need for young people, too — helping to fill the seats for Obama's address Thursday. With 6,000 delegates at the convention and thousands more attached to the event, Democrats hope to pack the nearly 74,000-seat outdoor stadium for the prime-time speech.

Obama has only fitfully defended his health care law from the bully pulpit since its enactment but on Sunday took it on directly. The president declared, as he has on occasion, that "I like the name" Obamacare despite its Republican origins as an insult.

"I do care," he said. "I don't know exactly what the other side is proposing; I guess you could call it 'Romney doesn't care.' But this law is here to stay." Republicans have rallied around the idea of repealing the law, although Romney has not laid out a detailed alternative.

Vice President Joe Biden joined the fray, accusing Republicans of seeking to undermine the decades-old federal program millions of seniors rely on for health care. "We are for Medicare," he said. "They are for voucher care." That was a reference to a proposal in Congress by Wisconsin Rep. Paul Ryan, the GOP vice presidential nominee, to offer future retirees the option of buying health insurance with a government subsidy.

The president and vice president campaigned separately across three battleground states as delegates descended on the Democrats' convention city before their first official meeting Tuesday in the Time Warner Cable Arena.

Some 800 demonstrators marched through the streets around Charlotte's convention hall, protesting what they call corporate greed as well as U.S. drone strikes overseas, said to kill children as well as terrorists. Dozens of police officers walked along with the protesters' parade, carrying gas masks, wooden batons and plastic hand ties. One arrest was reported, for public intoxication.

Biden's itinerary, in particular, underscored the threat that a sluggish recovery and high, 8.3 percent unemployment pose to Democrats seeking another term in power. He was in Pennsylvania and Wisconsin, states that have received little attention previously as the candidates, their parties and outside allies concentrate on the areas of the country deemed most competitive. His presence suggested the race in both states was tightening.

Obama's aides and allies flooded the weekend talk shows. All talked down Romney, but, when asked, none gave a clear answer to the classic campaign question: Are Americans better off than they were four years ago?

There is no rosy answer, given that Obama took office during a deep recession that ended in official terms six month later but yielded a paltry recovery with persistently high unemployment, now at 8.3 percent.

"No," Democratic Gov. Martin O'Malley said, before turning the blame to Obama's Republican predecessor. "But that's not the question of this election. The question, without a doubt — we are not as well off as we were before George Bush brought us the Bush job losses, the Bush recession, the Bush deficits, the series of desert wars."

Said Obama White House David Plouffe: "We've clearly improved ... from the depths of the recession."

And another aide, David Axelrod: "I think the average American recognizes that it took years to create the crisis that erupted in 2008 and peaked in January of 2009. And it's going to take some time to work through it."

But Democrats didn't miss a beat when it came to criticizing Romney and drawing contrasts between the convention that launched him into the last leg of the race and their own gathering ahead.

"This is not a reinvention convention like the Republican convention was last week," Obama campaign spokeswoman Jen Psaki said on the Air Force One flight to Ohio late Sunday. "We know that the convention is a huge platform with a big megaphone, and there is no question that next Friday, when the American people look back, they're going to know what the choice is, they're going to know what his forward-looking agenda is. "

She branded the Romney and GOP agenda an "empty pool with no water and dead leaves."

Romney spent Sunday at his Wolfeboro, N.H., vacation home, leaving only to attend church services with his wife, Ann. Aides said he would spend much of the Democrats' convention week preparing for three fall debates with Obama, beginning on Oct. 3.

Obama aides said they expected Romney and Republicans to outpace the president and his party in fundraising in August because Obama spent less time raising cash than in the month before and because the GOP held its convention — usually a big money draw — in August.

Biden, campaigning in York, Pa., on Sunday, took a swipe at Romney on foreign policy.

"He said it was a mistake to end the war in Iraq and bring all of our warriors home," the vice president said. "He said it was a mistake to set an end date for our warriors in Afghanistan and bring them home. He implies by the speech that he's ready to go to war in Syria and Iran. "

Democrats have been critical of Romney for making no mention of the war in Afghanistan when he accepted the Republican nomination in Tampa, Fla., last week. He previously criticized Obama for setting a public date for the withdrawal of U.S. combat troops from the war.

Romney also has faulted Obama for allowing the government of Syrian President Bashar Assad to remain in power. Yet his aides have refused to say for a week if he agrees with French President Francois Hollande's promise to extend diplomatic recognition to a provisional government if Syrian rebels form one.

At the Democratic convention, San Antonio Mayor Julian Castro delivers the keynote speech on Tuesday, followed by first lady Michelle Obama's remarks. Obama and Biden will be nominated for second terms on Wednesday night, when former President Bill Clinton takes the stage as star speaker. Biden and Obama close the convention Thursday night with their nomination acceptance speeches.